@media media-type and (media-feature-rule) {
    /* CSS rules go here */
}

/* 媒体类型 */
/* media-type {
    all | aural | braille | handheld | print | projection | screen | tty | tv | embossed| speech;
} */

/* 
*全部
all; 
*听觉
aural; 
*盲文
braille; 
*手持设备
handheld; 
*打印
print; 
*屏幕
screen; 
*语音
speech; 
*浮雕印刷
embossed; 
*电视
tv; 
*投影
projection; 
*终端
tty; 
 */



/* 媒体属性 */
/* media-feature-rule{
    width | height | device-width | device-height | orientation | aspect-ratio | device-aspect-ratio;
} */


/* 宽 */
/* width::after | before;  */
/* 高 */
/* height::after | before;  */
/* 设备宽 */
/* device-width::after | before;  */
/* 设备高 */
/* device-height::after | before;  */
/* 横屏 | 竖屏 */
/* orientation: landscape | portrait;  */
/* 宽高比 */
/* aspect-ratio::after | before;  */
/* 设备宽高比 */
/* device-aspect-ratio::after | before;  */